The present invention relates to a focused ion beam apparatus to perform ion beam processing, such as film processing, etch processing, selective etch processing or the like, when a focused ion beam is scanned to a predetermined region of a sample placed in a vacuum tank while simultaneously blowing an assist gas to the predetermined region.
In a focused ion beam apparatus using an assist gas, a sublimate substance in a solid or powder form packed as an assist gas material within a reservoir. The reservoir is heated up and the pressure inside the reservoir is controlled. The assist gas under pressure control is passed through a valve and supplied to a vacuum tank through an gas injector. The flow rate of the gas from the gas injector is determined by reservoir pressure, gas injector conductance and vacuum tank pressure. Accordingly, the flow rate of the gas through the gas injector is controlled by controlling the reservoir pressure constant.
Also, for the substance having a vapor pressure of 400 Torr or higher at room temperature (20 degrees), the flow rate of an assist gas is controlled by a mass flow controller or control valve for vacuum degree control. The assist gas is passed through the valve and supplied to the gas injector through a gas injector.
Problems that the Invention is to Solve
The conventionally implemented reservoir gas supply system for a focused ion beam apparatus using an assist gas, the pressure is controlled by utilizing material gas vapor pressure. Accordingly, the high vapor pressure material that is gaseous or liquidated form at room temperature could not be employed as a material for an assist gas.
Also, even if a mass flow controller be used, the flow rate was difficult to control at constant where a primary pressure and a secondary pressure had a low differential pressure or the flow rate was slight in amount.
In order to solve the above problem, the reservoir or the like is cooled/controlled to a constant temperature of xe2x88x9250xc2x0 C. or below so that the assist gas material has a vapor pressure usable in a low state. An assist gas controlled in flow rate is supplied to an inside of a vacuum tank.